bignum

Most computer languages provide a type of data called
"integer", but such computer integers are usually limited in
size; usually they must be smaller than 2^31 (2,147,483,648)
or (on a bitty box) 2^15 (32,768). If you want to work with
numbers larger than that, you have to use floating-point
numbers, which are usually accurate to only six or seven
decimal places. Computer languages that provide bignums can
perform exact calculations on very large numbers, such as
1000! (the factorial of 1000, which is 1000 times 999 times
998 times ... times 2 times 1). For example, this value for
1000! was computed by the MacLISP system using bignums: